Light curable dental composition

ABSTRACT

A light curable dental composition is provided. The composition comprises an ethylenic unsaturated compound and a light polymerization initiator. The light polymerization initiator is selected from a combination of an organic peroxide and a pyrylium salt compound of: ##STR1## Wherein R 1 , R 2 , and R 3  each represents a hydrogen atom, an alkyl group and the like, X stands for an oxygen or sulfur atom and Y for an anionic functional group; a polyperoxy ester containing a benzophenone group; and a combination the polyperoxy ester and an α-diketone.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a light curable dentalcomposition, and more particularly to a dental composition which can becured by irradiation of light to be utilized for teeth crown materials,denture base materials, dental cementing materials, dental bondingmaterials, dental filling materials, dental impression materials andcaries-preventive materials.

2. Related Art Statements

Heat-polymerizable dental compositions wherein organic peroxides, suchas benzoyl peroxide, are used as the polymerization initiators andcold-setting type dental compositions wherein Redox type polymerizationinitiators, such as a combination of benzoyl peroxide with a tertiaryamine, are used as the polymerization initiators have been known in theart. Further known in the art is a composition containing a sensitizersuch as benzoin alkyl ether to be cured by irradiation of ultravioletrays.

However, the known heat-polymerizable and cold-setting type dentalcompositions have a disadvantage that the cured resins tend to containair bubbles to lower the mechanical strengths and water-proofproperties, since they are prepared by mixing a powder with a liquid orkneading a paste with another paste. In addition, the heat-polymerizabledental compositions have another disadvantage that a complicate andtime-consuming operation is required for polymerization. On the otherhand, the cold-setting type dental compositions have additionaldisadvantages that the curing speed thereof is too high to causedifficulties in clinical operation, and that the formed denture iscolored to deteriorate the appearance due to the undesirous action bythe tertiary amine.

The composition containing an ordinary light polymerization initiatorsensitive to ultraviolet rays, such as benzoin alkyl ether, gives riseto problems that the transmittance to ultraviolet rays effective topolymerization or curing is so low as to limit the depth of curedcomposition only to less than 2 mm resulting in unsatisfactory curingdepth, that a filter or other protection means is indispensable sincethe ultraviolet rays contain the rays having wavelengths of less than320 nm which are harmful to human being, and that the lifetime of amercury lamp used as the irradiation source is short so that the lamp isdamaged soon.

Further known in the art is an one-paste type dental compositioncontaining a light polymerization initiator. However, the known dentalcomposition of this type has disadvantages that the mechanicalstrengths, particularly the bending strength, of the cured product islow, and that it is inferior in handling ease or operation facility whenused in practical operation.

OBJECTS AND SUMMARY OF THE INVENTION

A primary object of this invention is to provide a light curable dentalcomposition which can be readily cured by irradiation of light within ashort time period to give a cured product which is set deep in theinterior region thereof.

Another object of this invention is to provide a light curable dentalcomposition which is inexpensive and excellent in curing property, andyet ensures safe and easy operation in clinical application.

A further object of this invention is to provide a light curable dentalcomposition which forms a colorless cured product of clear appearance.

A still further object of this invention is to provide a light curabledental composition which has a surface of lower adhesiveness to make thehandling in clinical operation easier and forms a cured product havinghigher mechanical strengths including the bending strength.

The above and other objects of the invention will become apparent fromthe following description.

A light curable dental composition provided in accordance with thepresent invention comprises an ethylenic unsaturated compound and alight polymerization initiator, said light polymerization initiatorbeing selected from the group consisting of:

(a) a combination of an organic peroxide and a pyrylium salt compoundrepresented by the following general formula [I] of: ##STR2## whereinR₁, R₂ and R₃ each represents the same or different atom or group andstands for a hydrogen atom, a halogen atom, an alkyl group, a haloalkylgroup, an ethylenyl group, a styryl group, an alkoxy group, a phenylgroup, a naphthyl group, an alkylphenyl group, an alkoxyphenyl group, ahydroxyphenyl group, a halophenyl group, a nitrophenyl group, anaminophenyl group, an alkylaminophenyl group, an alkylaminostyryl group,a nitro group, an amino group or a hydroxyl group, X stands for anoxygen atom or a sulfur atom and Y for an anionic functional group;

(b) a polyperoxy ester containing a benzophenone group and representedby the following general formula [II] of: ##STR3## wherein R₁ and R₁ 'each represents the same or different group and stands for a tertiaryalkyl group having 4 to 8 carbon atoms or a tertiary aralkyl grouphaving 9 to 12 carbon atoms and R₂ and R₂ ' each represents the same ordifferent atom or group and stands for a hydrogen atom, a tertiaryalkoxy group having 4 to 8 carbon atoms or a tertiary aralkyloxy grouphaving 9 to 12 carbon atoms; and

(c) a combination of said polyperoxy ester represented by the generalformula [II] and an α-diketone.

DESCRIPTION OF THE INVENTION

The present invention will be described in detail hereinbelow.

The light curable dental composition, according to the invention,comprises an ethylenic unsaturated compound and one or more of specificlight polymerization initiators.

Any ethylenic unsaturated compounds which have been conventionally usedin the dental compositions may be used conveniently in the compositionof the invention, the examples being derivatives of methacrylic acid,such as methyl methacrylate, 2-hydroxyethyl methacrylate,neopentylglycol dimethacrylate, 1,4-butanediol dimethacrylate,ethyleneglycol dimethacrylate, diethyleneglycol dimethacrylate,triethyleneglycol dimethacrylate, polyethyleneglycol dimethacrylate,propyleneglycol dimethacrylate, dipropyleneglycol dimethacrylate,tripropyleneglycol dimethacrylate, polypropyleneglycol dimethacrylate,tetromethylolmethane trimethacrylate, tetramethylolmethanetetramethacrylate, hexamethyleneglycol dimethacrylate,2,2-bis(4-methacryloxyphenyl)propane,2,2-bis(4-methacryloxyethoxyphenyl)propane,2,2-bis(4-methacryloxypolyethoxyphenyl)propane,2,2-bis[4-(3-methacryloxy-2-hydroxypropoxy)phenyl]propane,1,2-bis(3-methacryloxy-2-hydroxypropoxy)ethane,2,2-bis(4-methacryloxyphenyl)propane,2-hydroxy-1,3-dimethacryloxypropane,di-2-methacryloxyethyl-2,2,4-trimethylhexamethylene dicarbamate,2-hydroxy-3-phenoxypropyl methacrylate,2-hydroxy-3-p-t-butylphenoxypropyl methacrylate,methacryloxyethylphenylphospholic acid, 4-methacryloxyethyl trimellitateanhydride and mixtures thereof. Other derivatives of acrylic acid,styrene and derivatives of styrene may also be used in the presentinvention. Curable resins having maleate, fumarate, allyl or(meth)acrylate groups, unsaturated polyester resins, unsaturated acrylicresins, or acrylate oligomers modified with isocyanate, polyester-acryloligomers, polyether-acryl oligomers, etc. may be used in the presentinvention.

The specific light polymerization initiator which may be used in theinvention is selected from the group consisting of:

(a) a combination of an organic peroxide and a pyrylium salt compoundrepresented by the following general formula [I] of: ##STR4## whereinR₁, R₂ and R₃ each represents the same or different atom or group andstands for a hydrogen atom, a halogen atom, an alkyl group, a haloalkylgroup, an ethylenyl group, a styryl group, an alkoxy group, a phenylgroup, a naphthyl group, an alkylphenyl group, an alkoxyphenyl group, ahydroxyphenyl group, a halophenyl group, a nitrophenyl group, anaminophenyl group, an alkylaminophenyl group, an alkylaminostyryl group,a nitro group, an amino group or a hydroxyl group, X stands for anoxygen atom or a sulfur atom and Y for an anionic functional group;

(b) a polyperoxy ester containing a benzophenone group and representedby the following general formula [II] of: ##STR5## wherein R₁ and R₁ 'each represents the same or different group and stands for a tertiaryalkyl group having 4 to 8 carbon atoms or a tertiary aralkyl grouphaving 9 to 12 carbon atoms and R₂ and R₂ ' each represents the same ordifferent atom or group and stands for a hydrogen atom, a tertiaryalkoxy group having 4 to 8 carbon atoms or a tertiary aralkyloxy grouphaving 9 to 12 carbon atoms; and

(c) a combination of the polyperoxy ester represented by the generalformula [II] and an α-diketone.

Initially, the light polymerization initiator which is the combinationof an organic peroxide and a pyrylium salt compound represented by theaforementioned general formula [I] will be described.

A single or a combination of two or more organic peroxides, each havingone or more oxygen-oxygen bonds in one molecule, may be used in theinvention, the specific examples being methyl ethyl ketone peroxide,cyclohexanone peroxide, acetylacetone peroxide,1,1-bis(t-butylperoxy)cyclohexane, t-butylhydroperoxide, cumenehydroperoxide, diisopropylbenzene hydroperoxide, p-methanehydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, dicumylperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, acetyl peroxide,octanoyl peroxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide,benzoyl peroxide, diisopropylperoxy dicarbonate, di-2-ethylhexylperoxydicarbonate, di(3-methyl-3-methoxybutyl)peroxy dicarbonate,t-butylperoxy isobutylate, t-butylperoxy octanoate, t-butylperoxybenzoate, di-t-butyldiperoxy isophthalate,2,5-dimethyl-2,5-di(benzoylperoxy)hexane,3,3',4,4'-tetra(tertiarybutylperoxycarbonyl)benzophenone,tri(t-butylperoxy)trimellitate,3,3',4,4'-tetra-(t-amylperoxycarbonyl)benzophenone,3,3',4,4'-tetra-(t-hexylperoxycarbonyl)benzophenone,3,3',4,4'-tetra-(t-octylperoxycarbonyl)benzophenone,3,3',4,4'-tetra-(cumylperoxycarbonyl)benzophenone,3,3',4,4'-tetra-(p-isopropylcumylperoxycarbonyl)benzophenone, andmixtures thereof.

A single or a combination of two or more pyrylium salt compounds may beused in the invention, and the examples of the pyrylium compound includepyrylium salts and thiopyrylium salts represented by the general formula[I] wherein the anionic functional group Y is perchlorate, fluoroborate,fluorophosphonate, fluoroantimonate, chloroaluminate, sulphuracetate,methosulfate, thiocyanate, sulfate, nitrate or acetate.

The specific examples of the compounds represented by the generalformula [I] will be listed as follows:

4-(4-butoxyphenyl)-2,6-bis(4-methoxyphenyl)pyrylium fluoroborate,

4-(4-butoxyphenyl)-2,6-diphenylthiopyrylium fluoroborate,

4-(4-butoxyphenyl)-2,6-bis(4-methoxyphenyl)thiopyrylium fluoroborate,

2,6-bis(4-methoxyphenyl)-4-phenylthiopyrylium fluoroborate,

4-(4-butoxyphenyl)-2,6-diphenylpyrylium fluoroantimonate,

2-methyl-4,6-bis(4-methoxyphenyl)thiopyrylium fluoroborate,

2,4,6-tri(4-methoxyphenyl)thiopyrylium perchlorate,

2,4,6-tri(4-methoxyphenyl)thiopyrylium fluoroborate,

4-(3,4-diethoxyphenyl)-2,6-bis(4-methoxyphenyl)thiopyryliumfluoroborate,

4-(4-dimethylaminophenyl)-2,6-diphenylthiopyrylium perchlorate,

2-nitro-4,6-bis(4-dimethylaminostyryl)pyrylium fluoroborate,

2-methoxy-4-naphthyl-6-styrylthiopyrylium fluoroborate,

2-amino-4,6-bis(4-butoxyphenyl)thiopyrylium perchlorate,

2-(4-nitrophenyl)-4,6-bis(4-butylphenyl)thiopyrylium fluoroborate,

2-hydroxy-4,6-bis(4-dimethylaminostyryl)pyrylium perchlorate,

2-(3,4-dichlorophenyl)-4-(4-methoxyphenyl)-6-phenylpyryliumfluoroborate.

The pyrylium or thiopyrylium salt which acts as a sensitizer iscontained in the composition preferably in an amount of 0.0001 to 1 partby weight, more preferably 0.001 to 0.5 part by weight, based on 100parts by weight of the ethylenic unsaturated compound. If the content ofthe sensitizer is less than 0.0001 part by weight, the composition cannot be cured by irradiation of visible ray; whereas the content of thesensitizer in excess of 1 part by weight is undesirable for the reasonthat the thickness of cured layer (i.e. the depth of curing) isconversely decreased and for hygienic reason.

Preferable content of the organic peroxide ranges within 0.001 to 10parts by weight, more preferably within 0.01 to 5 parts by weight, basedon 100 parts by weight of the ethylenic unsaturated compound. If thecontent of the organic peroxide is less than 0.001 part by weight, thecomposition is not curable, whereas the content thereof in excess of 10parts by weight is undesirable because of the deterioration of theproperties of the cured product.

When a combination of the organic peroxide and the sensitizer is used asthe light polymerization initiator, the composition may be readily curedby irradiation of a visible ray having a wavelength of from 400 nm to700 nm for a short time so that the depth of curing reaches not lessthan 5 mm to make the composition well adapted for dental uses.

The light polymerization initiator which is a polyperoxy estercontaining a benzophenone group and represented by the aforementionedgeneral formula [II] will now be described in detail. The polyperoxyesters represented by the general formula [II] wherein the carbon numberin either of R₁ or R₁ ' exceeds 9 are inferior in polymerizationinitiating function due to depression in active oxygen emission.Likewise, the polyperoxy esters represented by the general formula [II]wherein the carbon number in either of R₂ or R₂ ' exceeds 13 areinferior in polymerization initiating function. A single or acombination of two or more polyperoxy esters containing a benzophenonegroup and represented by the general formula [II] may be used in theinvention, and the specific examples thereof include3,3',4,4'-tetra-(t-butylperoxycarbonyl)benzophenone,3,3',4,4'-tetra-(t-amylperoxycarbonyl)benzophenone,3,3',4,4'-tetra-(t-hexylperoxycarbonyl)benzophenone,3,3',4,4'-tetra-(t-octylperoxycarbonyl)benzophenone,3,3',4,4'-tetra-(cumylperoxycarbonyl)benzophenone,3,3',4,4'-tetra-(p-isopropylcumylperoxycarbonyl)benzophenone,3,3'-dicarboxy-4,4'-di(t-butylperoxycarbonyl)benzophenone,3,3'-dicarboxy-4,4'-di(t-hexylperoxycarbonyl)benzophenone and mixturesthereof.

The concentration of the polyperoxy ester containing a benzophenonegroup and acting as a light polymerization initiator ranges preferablywithin 0.01 to 10 parts, more preferably within 0.05 to 5 parts, byweight, based on 100 parts by weight of the ethylenic unsaturatedcompound. If the concentration of the light polymerization initiator isless than 0.01 part by weight, the composition is not curable. On thecontrary, if the concentration of the light polymerization initiator ismore than 10 parts by weight, the properties of cured product areadversely deteriorated. When a polyperoxy ester containing abenzophenone group is used as the light polymerization initiator, thecomposition may be readily cured by irradiation of a harmless ray havinga wavelength of from 350 nm to 450 nm within a short time period to forma colorless and beutiful cured product.

The light polymerization initiator which is a combination of thepolyperoxy ester containing a benzophenone group and represented by theaforementioned general formula [II] and an α-diketone will now bedescribed in detail. In this case, a single or a mixture of two or morepolyperoxy esters each having a benzophenone group may be combined witha single or a mixture of two or more α-diketones. Any α-diketones may beused as far as they have a peak absorption at a wavelength of 400 nm to700 nm, the specific examples being biacetyl, 2,3-pentadione,2,3-octadione, bonzyl, 4,4'-dimethoxybenzyl, 4,4'-oxybenzyl,4,4'-dichlorobenzyl, acenaphthenequinone, 9,10-phenanthrenequinone,camphorquinone and β-naphthoquinone. Any one or a mixture of theα-diketones may be used. Particularly preferred α-diketones areacenaphthenequinone, 9,10-phenanthrenequinone, camphorquinone andβ-naphthoquinone.

The concentration of the α-diketone ranges preferably within 0.01 to 10parts by weight, more preferably within 0.1 to 5 parts by weight, basedon 100 parts by weight of the ethylenic unsaturated compound. If theconcentration of α-diketone is less than 0.01 part by weight, noappreciable effect is provided by the addition of α-diketone. On thecontrary, if the concentration of α-diketone is more than 10 parts byweight, not all of the added α-diketone is dissolved in the compositionor the depth of curing is decreased, in addition to undesirable hygienicinfluence.

The concentration of the polyperoxy ester having a benzophenone groupranges preferably within 0.01 to 10 parts by weight, more preferablywithin 0.1 to 5 parts by weight, based on 100 parts by weight of theethylenic unsaturated compound. If the concentration of the polyperoxyester having a benzophenone group is less than 0.01 part by weight, noappreciable effect is provided by the addition of polyperoxy esterhaving a benzophenone group. On the contrary, if the concentration ofthe polyperoxy ester having a benzophenone group is more than 10 partsby weight, not all of the added polyperoxy ester is dissolved in thecomposition or the properties of the cured product are deteriorated, inaddition to undesirable hygienic influence.

When a combination of the α-diketone and the polyperoxy ester having abenzophenone group is used as the light polymerization initiator, thecomposition may be readily cured by irradiation of a visible ray havinga wavelength of from 400 nm to 700 nm for a short time period in a depthof curing of not less than 4 mm so that the composition can be welladapted for curable dental applications.

The light curable dental composition, according to the invention, maycontain fine particles of inorganic filler with or without the additionof high polymer surface active agent. Preferable inorganic filler usedfor this purpose include apatite, soda-lime glass, silica, quartz,borosilicate glass, alumina, barium oxide, zirconium glass and mixturesthereof. A particularly preferred inorganic filler is a silica having anaverage particle size of from 1 to 100 millimicrons and being treated tobe hydrophobic with a treating agent, such as dimethyldichlorosilane,hexamethyldisilazane, octyltrimethoxysilane or silicone oils, becausesuch silica is improved in light transmittance, water-proof property andthixotropy.

High polymer surface active agents which may be added to the compositionof the invention include copolymers each being prepared bycopolymerizing an unsaturated monomer represented by the followinggeneral formula [III] of: ##STR6## wherein R₁ is a hydrogen atom or amethyl group,

R₂ is an alkyl group having 1 to 4 carbon atoms or a phenyl group, and nis an integer of 1 to 15;

with an unsaturated ester copolymerizable with the monomer representedby the general formula [III]. The copolymers prepared from unsaturatedmonomers represented by the general formula [III] wherein n exceeds 15are noot preferred, since they become so hydrophilic as to have lowerwater-proof property of the product composition.

The specific examples of the unsaturated monomer represented by thegeneral formula [III] are methoxyethyl (meth)acrylate,phenoxyethyloxyethyl (meth)acrylate, methoxydiethyleneglycol(meth)acrylate, methoxytetraethyleneglycol (meth)acrylate,isobutoxytetraethyleneglycol (meth)acrylate, methoxypolyethyleneglycol(meth)acrylate, ethoxypolyethyleneglycol (meth)acrylate,isopropoxypolyethyleneglycol (meth)acrylate, isobutoxypolyethyleneglycol(meth)acrylate, phenoxypolyethyleneglycol (meth)acrylate and mixturesthereof. In the specific examples listed above, "poly" means that nindicating the number of respective repeating unit ranges within 5 to15.

Examples of the unsaturated ester copolymerizable with theaforementioned monomer [III] are (meth)acrylic esters such as methyl(meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl(meth)acrylate and mixtures thereof.

The aforementioned copolymers may be prepared through ordinary solutionpolymerization, suspension polymerization or emulsion polymerizationwhile using a radical polymerization initiator. The molecular weight ofthe copolymer ranges preferably from 10 to 500 thousands inconsideration of solubility and lower adhesiveness.

The composition of the invention containing fine particles of aninorganic filler and a high polymer surface active agent selected fromthe copolymers listed above, may be conveniently used as a denture basematerial and as a dental impression material. It is desirous that 30 to80 parts by weight of one or more of the ethylenic unsaturated compoundsare mixed with 50 to 10 parts by weight of fine particles of one or moreof the aforementioned inorganic fillers and 0.1 to 20 parts by weight ofone or more of the aforementioned copolymers acting as effective surfaceactive agents. The compositions outside of the aforementioned mixingrange are inconvenient since they form sticky pastes or form pasteswhich are too low in viscosity to lose integrity for maintaining astable shape, or eventually they cannot form pastes. The compositioncontaining the dental filling material and the surface active agent, asaforementioned, provides a dental composition of paste form which has apertinent viscosity and a low surface tackiness to be adapted for easyapplication in clinical operation, and is cured to form a cured masshaving excellent mechanical strengths, particularly superior in bendingstrength.

Any of the dental compositions prepared in accordance with the presentinvention, irrespective of the particular light polymerization initiatorselected from the group defined in the appended claims with or withoutthe addition of the fine particles of any one or more inorganic fillersand high polymer surface active agents, may be further added with anadditional dental filling material which has been ordinarily used indental application. Examples of such a dental filling material areapatite, soda-lime glass, silica, quartz, silica gel, borosilicateglass, synthetic sapphire (alumina) and radioactive opaque fillingmaterials, such as barium oxide and zirconium glass. The dental fillingmaterial may be in the form of beads, micro-powders, micro-plates,fibers or whiskers, or may have irregular shapes. In addition to theaforementioned ingredients, an appropriate amount of other dentaladditives, such as binder resin, polymerization inhibitor, antioxidant,stabilizer, pigment, dye or viscosity increasing agent, may be added, asdesired.

The dental composition of the invention may be mixed by a manufacturer,charged in a sealed container in the form of a composite liquid orpaste, and supplied to a dentist or a dental technician. A dentist ordental technician may apply or fill the dental composition of theinvention thus supplied to mold the same, and then the composition isirradiated by a light from an irradiation source to be polymerized andcured.

Any irradiation sources may be used for curing the composition of theinvention as far as they generate lights having wavelengths within theaforementioned range, examples being a xenon lamp, a halogen lamp, atungsten lamp, a fluorescent lamp, a metal halide lamp and a laser.

The dental composition of the invention can be cured readily byirradiation of light within a short time period to be cured deeper inthe interior region and is superior over the conventional compositionusing a polymerization initiator sensitive to ultraviolet rays. Thedental composition of the invention is further improved in safe and easyhandling in clinical operation and in economical viewpoint.

EXAMPLES OF THE INVENTION

The present invention will now be described more specifically byreferring to examples and comparative examples. It should be noted herethat the following examples are given by way of example only, and thepresent invention is not limited thereby.

EXAMPLES 1 TO 10

Each of the compositions, as set forth in Table 1, was prepared bydissolving the organic peroxide and the sensitizer in the ethylenicunsaturated compound. The composition was filled in a polyethylenecylinder having an inner diameter of 10 mm and a depth of 10 mm, andexposed to visible light ray irradiation from a halogen lamp (150 watts,Maximum Irradiation Wavelength: 490 nm) placed above the cylinder by 3mm to be polymerized and cured. The depth of curing of each compositionwas measured using a micrometer after the polymerized and cured mass wasrecovered from the cylinder and the unreacted material was removedtherefrom. The results are shown in Table 1.

As should be appreciated from the results set forth in Table 1, thedental compositions of the invention were cured deep in the interiorregion (to have a depth of curing of not less than 5 mm) by exposure tovisible lights for a short time period of about 20 to 40 seconds to beadapted for use as excellent teeth crown materials, denture basematerials, dental cementing repair materials and dental impressionmaterials while being improved in handling ease in clinical operation.

COMPARATIVE EXAMPLE 1

A test sample was prepared by using 100 parts by weight oftriethyleneglycol dimethacrylate as the ethylenic unsaturated compound,2.0 parts by weight of di-t-butylperoxy isophthalate as the organicperoxide, and 0.5 part by weight of benzoinisobutyl ether as thesensitizer without the addition of a pyrylium salt compound. The otherprocedures were similar to Examples 1 to 10. The test sample was notcured after being exposed to light irradiation for 180 seconds, afterall. The result revealed that the composition containing a conventionalsensitizer sensitive to ultraviolet rays was not cured by exposure tovisible light irradiation.

                                      TABLE 1                                     __________________________________________________________________________           Ethylenic Unsaturated                                                                      Organic       Exposure                                                                           Depth of                                      Compound*.sup.1                                                                            Peroxide*.sup.2                                                                      Sensitizer*.sup.3                                                                    Time Curing                                        (part by wt.)                                                                              (part by wt.)                                                                        (part by wt.)                                                                        (sec)                                                                              (mm)                                   __________________________________________________________________________    Example 1                                                                            3G 100       LPO 1.0                                                                              BMTF 0.010                                                                           20   7.2                                    Example 2                                                                            3G 100       BPO 1.0                                                                              BMPF 0.010                                                                           30   5.0                                    Example 3                                                                            3G 100       PBIF                                                                              2.0                                                                              BMTF 0.010                                                                           35   6.5                                    Example 4                                                                            3G 100       TBB 2.0                                                                              BMPF 0.010                                                                           40   6.5                                    Example 5                                                                            3G 50 & bis-GMA 50                                                                         PBIF                                                                              1.5                                                                              BMTF 0.012                                                                           30   6.3                                    Example 6                                                                            3G 50 & bis-GMA 50                                                                         TBB 2.0                                                                              BMTF 0.005                                                                           20   7.5                                    Example 7                                                                            3G 50 & bis-GMA 50                                                                         PH25Z                                                                             2.0                                                                              BMTF 0.010                                                                           35   6.2                                    Example 8                                                                            bis-GMA 50 & UDMA 50                                                                       TBB 1.5                                                                              MPTF 0.010                                                                           20   7.3                                    Example 9                                                                            bis-GMA 50 & HMDA 50                                                                       PBIF                                                                              2.0                                                                               APTP 0.005                                                                          30   6.3                                     Example 10                                                                          HDMP 100     TBB 1.0                                                                               BPPA 0.020                                                                          30   6.4                                    __________________________________________________________________________     Note:                                                                         *.sup.1 3G: Triethylenglycol Dimethacrylate                                   bisGMA: 2,2Bis[43-methacryloxy-2-hydroxypropoxy)phenyl]propane                UDMA: Di2-methacryloxyethyl-2,2-4-trimethylhexamethylene Dicarbamate          HMDA: Hexamethyleneglycol Dimethacrylate                                      HDMP: 1,2Bis(3-methacryloxy-2-hydroxypropoxy)ethane                           *.sup.2 LPO: Lauroyl Peroxide                                                 BPO: Benzoyl Peroxide                                                         PBIF: Dit-butyldiperoxy Isophthalate                                          TBB: 3,3',4,4Tetra(t-butylperoxycarbonyl) Benzophenone                        PH25Z: 2,5Dimethyl-2-5-di(benzoylperoxy)hexane                                *.sup.3 BMTF: 4(4-Butoxyphenyl)-2,6-bis(4-methoxyphenyl)thiopyrylium          Fluoroborate                                                                  BMPF: 4(4-Butoxyphenyl)-2,6-bis(4-methoxyphenyl) pyrilium Fluoroborate        MPTF: 2,6Bis(4-methoxyphenyl)-4-phenylthiopyrilium Fluoroborate               APTP: 4(4-Dimethylaminophenyl)-2,6-diphenylthiopyrylium Perchlorate           BPPA: 4(4-Butoxyphenyl)-2,6-diphenylpyrylium Fluoroantimonate            

EXAMPLES 11 to 20

Each of the compositions, as set forth in Table 2, was prepared bydissolving the light polymerization initiator in the ethylenicunsaturated compound to prepare a dental composition. The compositionwas filled in a polyethylene cylinder having an inner diameter of 10 mmand a depth of 10 mm, and exposed to light ray irradiation from ahalogen lamp (15 volts, 150 watts) placed above the cylinder by 3 mm,while filtering off the light rays having wavelengths of less than 350nm, to be polymerized and cured. The depth of curing of each compositionwas measured using a micrometer after the polymerized and cured mass wasrecovered from the cylinder and the unreacted material was removedtherefrom. The results are shown in Table 2.

EXAMPLES 21 AND 22

Each of the compositions, as set forth in Table 2, was prepared bydissolving the light polymerization initiator uniformly in the ethylenicunsaturated compound, followed by adding a silica gel base filler(AEROSIL R 972 produced by Aerosil Nippon K.K.), and then kneaded bytwin rollers to obtain a dental composition. The depth of curing wasmeasured generally following the procedures as conducted in Examples 11to 20. The results are shown in Table 2.

As should be appreciated from the results set forth in Table 2, thedental compositions of the invention were cured deep in the interiorregion (to have a depth of curing of not less than 5 mm) by exposure tolights deprived of those having the wavelengths of less than 350 nm fora short time period of about 30 to 60 seconds to be adapted for use asexcellent teeth crown materials, denture base materials, dentalcementing repair materials, caries-preventive materials and dentalimpression materials while being improved in handling ease in clinicaloperation and having good appearance without coloring.

COMPARATIVE EXAMPLES 2 and 3

Similar tests, as in Examples 11 to 20, were conducted while usingtriethyleneglycol dimethacrylate as the ethylenic unsaturated compoundwhich was added with the polymerization initiators as set forth in Table3.

As will be seen from the results set forth in Table 3, the compositioncontaining conventional light polymerization initiators sensitive toultraviolet rays are not curable even when they are exposed to lightrays deprived of the light fractions having the wavelengths of less than350 nm.

                                      TABLE 2                                     __________________________________________________________________________    Ethylenic Unsaturated                                                                            Light Polymeri-  Exposure                                                                           Depth of                             Compound*.sup.1    zation Initiator*.sup.2                                                                 Filler Time Curing                                                                             Color of                        (part by wt.)      (part by wt.)                                                                           (part by wt.)                                                                        (sec)                                                                              (mm) Cured Mass                      __________________________________________________________________________    Example 11                                                                          3G 100       TBB 1.0   --     30   5.0  colorless                       Example 12                                                                          3G 100       TAB 1.0   --     40   6.0  colorless                       Example 13                                                                          3G 100       THB 1.0   --     50   6.5  colorless                       Example 14                                                                          3G 100       TOB 1.0   --     60   7.1  colorless                       Example 15                                                                          3G 100       TCB 1.5   --     40   5.5  colorless                       Example 16                                                                          3G 100       .sup. TIB 2.0                                                                           --     40   5.8  colorless                       Example 17                                                                          3G 50 & bis-MEPP 50                                                                        TBB 1.0 & THB 0.2                                                                       --     30   5.1  colorless                       Example 18                                                                           HMDA 50 & UDMA 50                                                                         TBB 1.0 & CBP 0.1                                                                       --     40   6.1  colorless                       Example 19                                                                          TMM-3M 50 & HDMP 50                                                                        TBB 1.0 & CHP 0.1                                                                       --     50   6.6  colorless                       Example 20                                                                          3G 50 & bis-GMA 50                                                                         TBB 0.5   --     60   7.2  colorless                       Example 21                                                                          3G 25 & bis-GMA 25                                                                         TBB 1.5   40     60   6.5  colorless                       Example 22                                                                          3G 20 & bis-GMA 30                                                                         TBB 1.5   50     60   6.4  colorless                       __________________________________________________________________________     Note:                                                                         *.sup.1 bisMEPP: 2,2Bis(4-methacryloxyethoxyphenyl)propane                    TMM3M: Tetramethylolmethane                                                   The other abridged notations are the same as noted in the note of Table 1     *.sup.2 TBB: 3,3',4,4Tetra-(t-butylperoxycarbonyl)benzophenone                TAB: 3,3',4,4Tetra-(t-amylperoxycarbonyl)benzophenone                         THB: e,e',4,4Tetra-(t-hexylperoxycarbonyl)benzophenone                        TOB: 3,3',4,4Tetra-(t-octylperoxycarbonyl)benzophenone                        TCB: 3,3',4,4Tetra-(cumylperoxycarbonyl)benzophenone                          TIB: e,e',4,4Tetra-(p-iso ro ylcumylperoxycarbonyl)benzophenone               CBP: 3,3Dicarboxy-4,4di(t-butylperoxycarbonyl)benzophenone                    CHP: 3,3'Dicarboxy4,4di(t-hexylperoxycarbonyl)benzophenone               

                                      TABLE 3                                     __________________________________________________________________________                Ethylenic Unsaturated                                                                    Light Polymerization                                                                     Exposure                                                                           Depth of                                           Compound   Initiator  Time Curing                                             (part by wt.)                                                                            (part by wt.)                                                                            (sec)                                                                              (mm)                                   __________________________________________________________________________    Comparative Example 2                                                                     3G 100      BF* 1.0   60   0                                      Comparative Example 3                                                                     3G 100     BIE** 1.0  60   0                                      __________________________________________________________________________     Note:                                                                         *BF: Benzophenone                                                             BIE: Benzoinisobutyl Ether                                                    The other abridged notations are the same as noted in the Note of Table 1                                                                              

EXAMPLES 23 TO 34

Each of the compositions, as set forth in Table 4, was prepared bydissolving the α-diketone and the polyperoxy ester containing abenzophenone group uniformly in the ethylenic unsaturated compound. Thecomposition was filled in a polyethylene cylinder having an innerdiameter of 10 mm and a depth of 10 mm, and exposed to visible light rayirradiation from a halogen lamp (15 volts, 150 watts) placed above thecylinder by 3 mm to be polymerized and cured. In order to learn theprecise effect of irradiated light wavelength, the top of the cylinderfilled with the composition was covered with a color glass filterthrough which the visible light rays from the halogen lamp wasirradiated. The used color glass filters were Y-43 and Y-47 (produced byToshiba Co., Ltd.) which had, respectively, the limit transmissionwavelengths of 430 nm and 470 nm. The light intensity passing throughthe color glass filter was reduced to about one half to one third of theintensity of light emitted from the lamp. The depth of curing of eachcomposition was measured using a micrometer after the polymerized andcured mass was recovered from the cylinder and the unreacted materialwas removed therefrom. The results are shown in Table 4.

As should be appreciated from the results set forth in Table 4, thedental compositions of the invention were cured deep in the interiorregion (to have a depth of curing of not less than 5 mm) by exposure tovisible lights for a short time period of about 20 to 40 seconds. Itshould be also apparent from the results irradiated by light rayspassing through color glass filters that the compositions of theinvention can be effectively cured by extremely safe light rays havingthe wavelengths of not less than 470 nm although the intensity of lightrays passing through the filters is lowered to one half to one third ofthe light intensity originally emitted from the lamp. As will beunderstood from the foregoing, the dental compositions prepared inaccordance with the present invention have superior properties when usedas teeth crown materials, denture base materials, dental cementingrepair materials and dental impression materials while being improved inhandling ease and safety in clinical operation.

COMPARATIVE EXAMPLES 4 TO 7

Each test sample was prepared by mixing the components in the ratio asset forth in Table 5, and subjected to tests conducted similarly as inthe precedng Examples. As will be seen from the results shown in Table5, a composition merely containing an α-diketone or containing acombination of an α-diketones with an ordinary organic peroxide cannotbe cured by visile light rays to a satisfactory curing level.

                                      TABLE 4                                     __________________________________________________________________________    Ethylenic Unsaturated       Peroxy    Exposure                                                                           Depth of                           Compound*.sup.1    α-Diketone*.sup.2                                                                Ester*.sup.3                                                                            Time Curing                                                                             Color Glass                   (part by wt.)      (part by wt.)                                                                          (part by wt.)                                                                           (sec)                                                                              (mm) Filter                        __________________________________________________________________________    Example 23                                                                          3G 100       KQ 1.0   TBB 1.0   30   7.3  None                          Example 24                                                                          3G 100       KQ 1.0   TBB 1.0   40   4.6  Y-43                          Example 25                                                                          3G 50 & bis-GMA 50                                                                          PQ 0.1 & KQ 1.0                                                                       TBB 1.0 & TAB 0.5                                                                       20   5.5  None                          Example 26                                                                          3G & bis-GMA 50                                                                             PQ 0.1 & KQ 1.0                                                                       TBB 1.0 & TAB 0.5                                                                       40   5.0  Y-47                          Example 27                                                                          bis-GMA 50 & UDMA 50                                                                       KQ 2.0   TBB 1.0 & THB 0.2                                                                       30   5.4  None                          Example 28                                                                          bis-GMA 50 & UDMA 50                                                                       KQ 2.0   TBB 1.0 & THB 0.2                                                                       40   4.0  Y-47                          Example 29                                                                          bis-GMA 50 & HMDA 50                                                                       AQ 0.1 & KQ 0.5                                                                        TBB 1.0 & TOB 1.0                                                                       30   7.3  None                          Example 30                                                                          bis-GMA 50 & HMDA 50                                                                       AQ 0.1 & KQ 0.5                                                                        TBB 1.0 & TOB 1.0                                                                       40   4.5  Y-43                          Example 31                                                                           .sup. 3G 50 & HDMP 50                                                                     KQ 1.5   TBB 0.5 & TCB 0.5                                                                       30   5.8  None                          Example 32                                                                           .sup. 3G 50 & HDMP 50                                                                     KQ 1.5   TBB 0.5 & TCB 0.5                                                                       40   4.2  Y-47                          Example 33                                                                          3G 100       BQ 0.1 & KQ 0.7                                                                        .sup. TBB 0.5 & TIB 0.1                                                                 25   6.5  None                          Example 34                                                                          3G 100       BQ 0.1 & KQ 0.7                                                                        .sup. TBB 0.5 & TIB 0.1                                                                 40   4.5  Y-43                          __________________________________________________________________________     Note:                                                                         *.sup.1 All of the abridged notations are the same as noted in the Note o     Table 1.                                                                      *.sup.2 KQ: Camphorquinone                                                    PQ: 9,10Phenanthrenequinone                                                   AQ: Acenaphthenequinone                                                       BQ: Naphtoquinone                                                             *.sup.3 All of the abridged notations are the same as noted in the Note o     Table 1.                                                                 

                                      TABLE 5                                     __________________________________________________________________________                Ethylenic Unsaturated                                                                    Light Polymerization                                                                    Exposure                                                                           Depth of                                            Compound   Initiator Time Curing                                                                             Color Glass                                    (part by wt.)                                                                            (part by wt.)                                                                           (sec)                                                                              (mm) Filter                             __________________________________________________________________________    Comparative Example 4                                                                     3G 100     KQ 1.0    40   0    Y-43                               Comparative Example 5                                                                     3G 100     KQ 1.0 & TBP* 1.0                                                                       40   0    Y-43                               Comparative Example 6                                                                     3G 100     KQ 1.0    20   0.2  None                               Comparative Example 7                                                                     3G 100     KQ 1.0 & TBP* 1.0                                                                       30   0.5  None                               __________________________________________________________________________     Note:                                                                         *TBP: tButylperoxybenzoate                                               

EXAMPLE 35 Preparation of High Polymer Surface Active Agent

Each of the copolymers (high polymer surface active agents) having thecompositions as set forth in Table 6 was synthesized by an ordinarysolution polymerization process while using benzene as the solvent and2,2'-azobisisobutylonitrile as the polymerization initiator. Eachcopolymer was precipitated in petroleum ether to obtain a solidcopolymer. The weight average molecular weights of respective copolymerswere determined by the GPC method. The results are shown in Table 6.

Preparation of Paste

Each of the light polymerization initiators and the copolymers, as setforth in Table 7, was dissolved in each mixture of ethylenic unsaturatedcompound to prepare a solution. The solution was charged in a kneaderand slowly added with fine particles of an inorganic filler, and theadmixture was kneaded at atmospheric pressure for 2 hours. The admixturewas kneaded under a reduced pressure of lower than 20 mmHg foradditional 2 hours to be defoamed, whereby a dental composition paste ofthe present invention was prepared.

Test

Each of the pastes having the compositions as set forth in Table 7 wasirradiated by a projector including four halogen lamps (150 watts) for apre-set time period to obtain a cured product. The tackiness of thesurface of the molded paste was observed by a finger touch test. Thebending strength of each cured product was measured by the method whichwill be described in detail hereinbelow.

Method for the Determination of Bending Strength

A cellophane sheet was laid over a stainless steel mold, and a paste wascharged and pressed on the cellophane sheet. The top face of the pastewas covered by another cellophane sheet, and then a slide glass platewas put thereon under a pressure to flatten the surface so that themolded paste had even side faces. Thereafter, the slide glass plate wasremoved, and the paste was exposed to irradiation of lights from the topface thereof for 2 minutes to be cured sufficiently. The cured productor resin was put out of the mold, and machined to form a test piecehaving a length of 60 mm, a width of 10 mm and a thickness of 2.5 mm.The test piece was aged for 24 hours after the light polymerization, andthen subjected to bending test. The span between the fulcra carrying thetest piece was set to 50 mm, and the bending strength of the test piecewas measured at a cross-head speed of 2 mm/min using a bending testerattached to an autograph. The bending strength was calculated from thefollowing equation of:

Bending Strength ##EQU1## wherein F is the maximum stress applied to thetest piece, I is the distance between the fulcra, b is the width of thetest piece, and d is the thickness of the test piece.

Bending strengths of five test pieces for each cured resin were measuredand the average value thereof was calculted. The results are shown inTable 7.

                                      TABLE 6                                     __________________________________________________________________________                                    Mixing Weight Average                         Copolymer                                                                           Composition               Ratio (wt %)                                                                         Molecular Weight                       __________________________________________________________________________    A     Methoxyethyl Methacrylate  5     113,000                                      Methoxydiethyleneglycol Monomethacrylate                                                                60                                                  Methyl Methacrylate       35                                            B     Methoxytetraethyleneglycol Monomethacrylate                                                             50     152,000                                      Methyl Methacrylate       45                                                  Ethyl Acrylate             5                                            C     Methoxytetraethyleneglycol Monomethacrylate                                                             45     108,000                                      Phenoxytetraethyleneglycol Monoacrylate                                                                  5                                                  Methyl Methacrylate       50                                            D     Isobutoxytriethyleneglycol Monomethacrylate                                                              5     120,000                                      Methoxypolyethyleneglycol Monomethacrylate (n = 9)                                                      25                                                  Methyl Methacrylate       70                                            __________________________________________________________________________

                                      TABLE 7                                     __________________________________________________________________________         Unsaturated                                                                            Fine Particles of Light Polymerization                                                                      Bending                           Ex. 35                                                                             Compound*.sup.1                                                                        Inorganic Filler*.sup.2                                                                Copolymer                                                                              Initiator*.sup.3                                                                          Strength                          Run No.                                                                            (part by weight)                                                                       (part by weight)                                                                       (part by weight)                                                                       (part by weight)                                                                          (kg/cm.sup.2)                                                                        Tackiness                  __________________________________________________________________________    1    3G 34    S-1 30   A 2      TBB      0.6                                                                              1110 ± 50                                                                         No                              MPEPP 34                   BMTF     0.006                                2    3G 30    S-1 38   B 2      TBB      0.6                                                                              1010 ± 80                                                                         No                              MPEPP 30                   BMTF     0.006                                3    3G 35    S-1 25   C 5      TBB      0.6                                                                              1150 ± 90                                                                         No                              MPEPP 35                   Camphorquinone                                                                         0.06                                 4    3G 34    S-2 30   D 2      TBB      0.6                                                                              1080 ± 50                                                                         No                              MPEPP 34                   Camphorquinone                                                                         0.06                                 5    3G 34    S-2 30   A 2      TBB      0.6                                                                               1220 ± 130                                                                       No                              MPEPP 34                   BMTF     0.006                                __________________________________________________________________________     Note:                                                                         *.sup.1 3G: Triethyleneglycol Dimethacrylate                                  MPEPP: 2,2Bis(4-methacryloxydiethoxyphenyl)propane                            *.sup.2 S1: Silica treated with dimethyldicholorosilane and having an         average particlesize of 20 millimicrons.                                      S2: Silica treated with hexamethyldisilazane and having an average            particle size of 15 millimicrons.                                             *.sup.3 TBB: 3,3',4,4Tetra-(t-butylperoxycarbonyl)benzophenone                BMTF: 4(4-Butoxyphenyl)-2,6-bis(4-methoxyphenyl)thiopyrylium Fluoroborate

Although the present invention has been described with reference to thespecific examples, it should be understood that various modificationsand variations can be easily made by those skilled in the art withoutdeparting from the spirit of the invention. Accordingly, the foregoingdisclosure should be interpreted as illustrative only and not to beinterpreted in a limiting sense. The present invention is limited onlyby the scope of the following claims.

What is claimed is:
 1. A light curable dental paste comprising anethylenic unsaturated compound, a light polymerization initiator, a highpolymer surface active agent and fine particles of an inorganic filler,said high polymer surface active agent being a copolymer which isprepared by copolymerizing an unsaturated monomer represented by thefollowing general formula (III) of: ##STR7## wherein R₁ is a hydrogenatom or a methyl group, R₂ is an alkyl group having 1 to 4 carbon atomsor a phenyl group, and n is an integer of 1 to 15; with an unsaturatedester copolymerizable with said monomer represented by the generalformula (III), said light polymerization initiator comprising acombination of an organic peroxide and a pyrylium salt compoundrepresented by the following general formula (I) of: ##STR8## whereinR₁, R₂ and R₃ each represents the same or different atom or group andstands for a hydrogen atom, a halogen atom, an alkyl group, a haloalkylgroup, an ethylenyl group, a styryl group, an alkoxy group, a phenylgroup, a naphthyl group, an alkylphenyl group, an alkoxyphenyl group, ahydroxyphenyl group, a halophenyl group, a nitrophenyl group, anaminophenyl group, an alkylaminophenyl group, an alkylaminostyryl group,a nitro group, an amino group or a hydroxyl group, X stands for anoxygen atom or a sulfur atom and Y for an anionic functional group.
 2. Acomposition as claimed in claim 1, wherein 0.0001 to 1 part, by weight,of said pyrylium salt compound is added to 100 parts, by weight, of saidethylenic unsaturated compound.
 3. A composition as claimed in claim 1,wherein 0.001 to 10 parts, by weight, of said organic peroxide is addedto 100 parts, by weight, of said ethylenic unsaturated compound.
 4. Acomposition as claimed in claim 1, wherein said ethylenic unsaturatedcompound is a derivative of methacrylic acid.
 5. A composition asclaimed in claim 4, wherein said derivative of methacrylic acid isselected from the group consisting of triethyleneglycol dimethacrylate,hexamethyleneglycol dimethacrylate,2,2-bis[4-(3-methacryloxy-2-hydroxypropoxy)phenyl]propane,di-2-methacryloxyethyl-2,2,4-trimethylhexamethylene dicarbamate,1,2-bis(3-methacryloxy-2-hydroxypropoxy)ethane, tetramethylolmethanetrimethacrylate, 2,2-bis(4-methacryloxyethoxyphenyl)propane,polypropyleneglycol dimethacrylate, methyl methacrylate,2,2-bis(4-methacryloxypolyethoxyphenyl)propane and mixtures thereof. 6.A composition as claimed in claim 1, wherein said organic peroxide is anorganic compound having one or more oxygen-oxygen bonds in one molecule.7. A composition as claimed in claim 6, wherein said organic peroxide isselected from the group consisting of lauroyl peroxide, benzoylperoxide, ditertiarybutyldiperoxy isophthalate,2,5-dimethyl-2,5-di(benzoylperoxy)hexane,3,3',4,4'-tetra-(tertiarybutylperoxycarbonyl)benzophenone,tertiarybutylperoxybenzoate, tri(tertiarybutylperoxy) trimellitate andmixtures thereof.
 8. A composition as claimed in claim 1, wherein saidpyrylium salt compound is selected from the group consisting of4-(4-butoxyphenyl)-2,6-bis(4-methoxyphenyl)pyrylium fluoroborate,4-(4-butoxyphenyl)-2,6-bis(4-methoxyphenyl)thiopyrylium fluoroborate,2,6-bis(4-methoxyphenyl)-4-phenylthiopyrylium fluoroborate,4-(4-butoxyphenyl)-2,6-diphenylpyrylium fluoroantimonate,4-(4-dimethylaminophenyl)2,6-diphenylthiopyrylium perchlorate,2,4,6-tri(4-methoxyphenyl)thiopyrylium fluoroborate and mixturesthereof.
 9. A composition as claimed in claim 1, wherein said inorganicfiller is selected from the group consisting of apatite, soda-limeglass, quartz, silica, borosilicate glass, alumina, barium oxide,zirconium glass and mixtures thereof.
 10. A composition as claimed inclaim 1, wherein said inorganic filler comprises silica and said silicahas an average particle size of from 1 to 100 millimicrons and istreated to be hydrophobic with a treating agent selected from the groupconsisting of dimethyldichlorosilane, hexamethyldisilazane,octyltrimethoxysilane and silicone oils.
 11. A composition as claimed inclaim 1, comprising 30 to 80 parts, by weight, of said ethylenicunsaturated compound, 10 to 50 parts, by weight, of said fine particlesof said inorganic filler and 0.1 to 20 parts, by weight, of saidcopolymer.
 12. A composition as claimed in claim 1, wherein saidunsaturated monomer represented by the general formula [III] is selectedfrom the group consisting of methoxyethyl acrylate, methoxyethylmethacrylate, methoxydiethyleneglycol acrylate, methoxydiethyleneglycolmethacrylate, methoxytetraethyleneglycol acrylate,methoxytetraethyleneglycol methacrylate, isobutoxypolyethyleneglycolacrylate, isobutoxypolyethyleneglycol methacrylate,methoxypolyethyleneglycol acrylate, methoxypolyethyleneglycolmethacrylate, phenoxypolyethyleneglycol acrylate,phenoxypolyethyleneglycol methacrylate and mixtures thereof.
 13. Acomposition as claimed in claim 1, wherein said unsaturated estercopolymerizable with said monomer represented by the general formula[III] is selected from the group consisting of acrylic esters,methacrylic esters and mixtures thereof.
 14. A composition as claimed inclaim 13, wherein said unsaturated ester copolymerizable with saidmonomer represented by the general formula [III] is selected from thegroup consisting of methyl acrylate, methyl methacrylate, ethylacrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate andmixtures thereof.
 15. A composition as claimed in claim 1, wherein saidperoxide used in combination with said pyrylium salt compound is apolyperoxy ester containing a benzophenone group and represented by thefollowing general formula [II] of: ##STR9## wherein R₁ and R₁ ' eachrepresents the same or different group and stands for a tertiary alkylgroup having 4 to 8 carbon atoms or a tertiary aralkyl group having 9 to12 carbon atoms and R₂ and R₂ ' each represents the same or differentatom or group and stands for a hydrogen atom, a tertiary alkoxy grouphaving 4 to 8 carbon atoms or a tertiary aralkyloxy group having 9 to 12carbon atoms.
 16. A composition as claimed in claim 1, wherein saidethylenic unsaturated compound is triethyleneglycol dimethacrylate, saidorganic peroxide is lauroyl peroxide and said pyrylium salt compound is4-(4-butoxyphenyl)-2,6-bis(4-methoxyphenyl)thiopyrylium fluoroborate.